Spoke recovery in a color display

ABSTRACT

Embodiments of the invention include a method, device and/or system for spoke recovery. A method for spoke recovery in a sequential multi-primary color display may include producing a primary color image component corresponding to a first primary color during a display period including at least a portion of a spoke period of the first primary color and a second primary color.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Filing Phase Application of InternationalApplication No. PCT/IL2004/00769, International Filing Date Aug.23,2004, which claims priority of U.S. Provisional Patent Application,60/497,561, Aug. 26, 2003.

FIELD OF THE INVENTION

The invention relates generally to color displays and, moreparticularly, to spoke recovery in color displays.

BACKGROUND

Various types of color display technologies are known in the art, forexample, projection display systems. In front projection displays, theprojected images are viewed from a reflective viewing screen. In rearprojection displays, the projected images are viewed through atransmissive viewing screen.

To produce color images, existing display devices use three primarycolors, typically red, green and blue, collectively referred to as RGB.In sequential projection display systems, a plurality of color filtersegments on a color wheel are sequentially introduced to the path oflight of a polychromatic beam to sequentially produce three primarycolor light beams. The primary color light beams are modulatedsequentially, for example, using a single Spatial Light Modulator (SLM)panel, and displayed on the reflective or transmissive viewing screen.

Such sequential RGB devices may have at least three transition regions(“spokes”), each formed between two adjacent color filter segments suchthat part of the polychromatic light beam passes through one colorfilter segment, and part of the light beam passes through an adjacentcolor filter segment. In such devices, the light passing through a spokemay produce a mixed color, e.g., a combination of the two primary colorsproduced by the adjacent filter segments. For example, a mixed red-greencolor may be produced in the spoke between the red and green filtersegments. Displaying the mixed color may distort the color of the viewedimage.

In order to avoid this effect, some systems prevent displaying the mixedcolors, e.g., by switching the SLM to an “off” mode of operation duringeach transition between two adjacent color segments, and/or by adding agenerally black or non-transparent segment between two successive filtersegments. However, in many implementations, the “spot size” of thepolychromatic light beam, i.e., the cross-sectional area of the lightbeam focused on the filter segments, may be relatively large, forexample, the spot size may span about 15 degrees out of the 360 degreesspan of the color wheel, whereby the spoke time between two adjacentfilter segments may be significant compared to the display time of theprimary color segments. Thus, switching the SLM to the “off” mode maysubstantially reduce the luminance of the display.

An important consideration in designing projection display devices isthe display brightness. Thus, efforts are continually made to increasethe optical efficiency of existing designs and, thereby, to increase theluminous output that can be obtained from a given light source.

In the display device described in U.S. Pat. No. 5,592,188 to Doherty etal., the SLM is not switched to the “off” mode during the spokes.Instead, the SLM is provided with “white image” data at the spokes,whereby a viewed white image is produced by a combination of the colorcomponents produced by all three spokes on the color wheel. This whiteimage may be utilized to enhance white areas of the color image.Although a correct color balance may be maintained by this solution, theadditional white light may reduce the color saturation of the displayedimage.

U.S. Pat. No. 6,567,134 to Morgan et al. describes a spoke lightrecovery method. The method includes calculating from primary color datarepresenting the color image special “secondary color” images, namely,yellow, cyan and magenta color components corresponding to threemixtures of primary color pairs. The method also includes providing thesecondary color image to the SLM during the spoke time between thecorresponding primary color segments.

The use of spoke light recovery in the devices described above requiresmanipulating the image input data in order to provide special signals,e.g. corresponding to the white/secondary color components.

In a more-than-three-primary sequential projection device, e.g., asdescribed in International Application PCT/IL01/00527, entitled “Device,System and Method For Electronic True Color Display”, filed Jun. 7,2001, and published Dec. 13, 2001 as WO 01/95544, assigned to theassignee of the present application, transition time becomes animportant factor affecting display luminance, since the number of colorfilter segments is increased compared to RGB projection displays.Furthermore, the spokes of such multi-primary displays do notnecessarily form a complementary set of colors.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Some exemplary embodiments of the present invention provide a colordisplay device implementing spoke recovery, e.g., to enhance luminancevalues of the primary colors.

The display device according to some exemplary embodiments of theinvention may implement spoke recovery without calculating anyadditional image components, e.g., white image components and/orsecondary color image components.

Some exemplary embodiments of the invention may be implemented inconjunction with a more-than-three primary color display device, forexample, a five-primary-color display device. The display device mayinclude a light source, a color switching mechanism, e.g., a colorwheel, having a plurality of color filters corresponding to a pluralityof primary colors, and a Spatial Light Modulator (SLM).

According to some exemplary embodiments of the invention, specificarrangements of the color filters and/or specific timing relationsbetween an input signal provided to the SLM and a color light beamproduced by the color filters may allow enhancement of the luminance ofthe primary colors. According to some exemplary embodiments of theinvention, the display device may include a controller to control thespatial light modulator to produce a primary color image componentcorresponding to a first primary color during a display period includingat least a portion of a spoke period of the first primary color and asecond primary color. The display period may further include at leastpart of a spoke period of the first primary color and a third primarycolor. The display period may have a desired distribution between thespoke period of the first and second primary colors and the spoke periodof the first and third primary colors.

According to some exemplary embodiments of the invention, the displayperiod may be distributed generally symmetrically between the spokeperiod of the first and second primary colors and the spoke period ofthe first and third primary colors.

According to some exemplary embodiments of the invention, the displayperiod may be represented by a plurality of bit planes including one ormore highest significance bit planes, wherein one or more of the highestsignificance bit planes correspond to at least one of the spoke periodof the first and second primary colors and the spoke period of the firstand third primary colors.

According to some exemplary embodiments, a most significant bit plane ofthe one or more highest significance bit planes may correspond to boththe spoke period of the first and second primary colors and the spokeperiod of the first and third primary colors.

According to some exemplary embodiments, a most significant bit plane ofthe one or more highest significance bit planes may correspond to afirst end of an electronic color interval including the spoke period ofthe first and second primary colors, and a second-most significant bitplane of the one or more highest significance bit planes may correspondto a second end of the electronic color interval including the spokeperiod of said first and third primary colors.

According to some exemplary embodiments, the controller is able tocontrol the spatial light modulator to produce a corrected succeedingprimary color image component corresponding to the third primary colorbased on a value of a most significant bit plane and a second-mostsignificant bit plane of the one or more highest significance bitplanes.

According to some exemplary embodiments, the display period may berepresented by a plurality of bit planes including at least one spokebit plane corresponding to at least one of the spoke period of the firstand second primary colors and the spoke period of the first and thirdprimary colors, wherein the at least one spoke bit plane represents atime period shorter than a predetermined time period threshold.

According to some exemplary embodiments, the controller is able tocontrol the spatial light modulator such that a viewed combination ofcolored light of the spoke period of the first and second primary colorsand colored light of the spoke period of the first and third primarycolors is generally equivalent to the first primary color.

According to some exemplary embodiments, the first, second and thirdprimary colors are yellow, green and red, respectively.

According to some exemplary embodiments, the first, second and thirdprimary colors are cyan, green and blue, respectively.

According to some exemplary embodiments, the first, second and thirdprimary colors are magenta, blue and red, respectively.

According to some exemplary embodiments, the color switching mechanismmay sequentially provide the spatial light modulator with colored lightof a plurality of primary colors. According to some exemplaryembodiments, at least three of the filters are arranged sequentiallyaccording to their hue values.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood and appreciated more fully from thefollowing detailed description of embodiments of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1 is a schematic, simplified isometric-view illustration of amulti-primary display device, in accordance with exemplary embodimentsof the invention;

FIG. 2 is a schematic illustration of an arrangement of five colorfilters on a color wheel, in accordance with exemplary embodiments ofthe invention;

FIG. 3 is a schematic illustration of a block diagram of an exemplaryimplementation of a method of inter-color gamma adjustment according toan exemplary embodiment of the invention;

FIG. 4A is a schematic illustration of graphs of five exemplary primarycolor wavelength spectra for a color display using the color wheel ofFIG. 2; and

FIG. 4B is a schematic illustration of chromaticity diagramsrepresenting a color gamut resulting from the five primary color spectraof FIG. 4A when spoke recovery is implemented, compared to a color gamutresulting from the five primary color spectra of FIG. 4A when spokerecovery is not implemented.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn accuratelyor to scale. For example, the dimensions of some of the elements may beexaggerated relative to other elements for clarity or several physicalcomponents included in one element. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements. It will be appreciatedthat these figures present examples of embodiments of the presentinvention and are not intended to limit the scope of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following description, various aspects of the present inventionwill be described. For purposes of explanation, specific configurationsand details are set forth in order to provide a thorough understandingof the present invention. However, it will be apparent to one skilled inthe art that the present invention may be practiced without the specificdetails presented herein. Furthermore, some features of the inventionrelying on principles and implementations known in the art may beomitted or simplified to avoid obscuring the present invention.

Embodiments of monitors and display devices with more than threeprimaries, in accordance with exemplary embodiments of the invention,are described in International Application PCT/IL01/00527, filed Jun. 7,2001, entitled “Device, System and Method For Electronic True ColorDisplay” and published Dec. 13, 2001 as PCT Publication WO 01/95544, thedisclosure of which is incorporated herein by reference.

Although some of the exemplary devices and/or methods described beloware described in the context of devices for reproducing five primarycolors, it may be appreciated by those skilled in the art, that similardevices and/or methods may be implemented, with appropriate changes, inconjunction with devices for reproducing more or less than five primarycolors. For example, a four-primary color display may include blue,green, yellow and red primary color filters, and may implement some ofthe methods described below for spoke recovery of one or both ofgreen-yellow and yellow-red spokes. A six-primary color display mayinclude blue, magenta, red, yellow, green and cyan primary colorfilters, and may implement some of the methods described below for spokerecovery of one or more of blue-magenta, magenta-red, green-yellow,yellow-red, green-cyan, and cyan-blue spokes.

Reference is made to FIG. 1, which is a schematic, simplifiedisometric-view illustration of a multi-primary display device 100adapted to reproduce a color image in accordance with exemplaryembodiments of the invention.

Display 100 may include a light source 102 adapted to producepolychromatic light, as is known in the art. For example, light source102 may include a high-pressure mercury lamp, e.g., a UHP™ lamp,available from Philips Lighting, a division of Royal Philips Electronicsof Eindhoven, Netherlands, or a Xenon (Xe) type light source, as isknown in the art. The device may also include a color switchingmechanism, e.g., a color wheel 104, having a plurality of color filters103 corresponding to a plurality of primary colors, as described below.Device 100 may also include a Spatial Light Modulator (SLM) 106, as isknown in the art.

The white light produced by light source 102 may be directed through anappropriate color filter of color wheel 104 in order to produce acorresponding color light beam of a defined spectral range, as describedbelow. For example, device 100 may include a condensing lens 105 tofocus the white light on the appropriate color filter. The color lightbeam may be directed, towards SLM 106, for example, using an extendinglens 107, as is known in the art. SLM 106 may modulate the color beam,in accordance with a primary color image component 119, to produce amodulated color light beam corresponding to a primary color imagecomponent, as described below. Signal 119 may be generated, e.g., by acontroller 121, using any of the methods described in theabove-referenced International Patent Application, e.g., by converting athree-primary-color image signal into a multi-primary-color imagesignal.

Color wheel 104 may be controllably rotated in the path of lightemanating from light source 102, e.g., using a motor 109, such that, forexample, in each rotation SLM 106 may be sequentially illuminated, e.g.,by all the colors on wheel 104. Thus, a plurality of modulated colorlight beams, e.g., each corresponding to one color image component, maybe produced by SLM 106, e.g., in each rotation of color wheel 104. Eachof the modulated color light beams may be projected by a projection lens108 onto a viewing screen 110. In some exemplary embodiments a polarizedbeam splitter 111 may be implemented in conjunction with SLM 106, asknown in the art. In some exemplary embodiments, the rate of rotationmay correspond to the frame frequency, i.e., the frequency at which thefull-color image on the viewing screen is refreshed. The human viewerintegrates the sequential stream of the primary color image componentsto obtain a full color image when viewing the image as projected ontothe viewing screen.

According to embodiments of the invention, specific arrangements of thecolor filters and/or specific timing relations between the input signalprovided to the SLM and the color light beam produced by the colorfilters may enhance the luminance of the primary colors, as describedbelow.

Reference is also made to FIG. 2, which schematically illustrates anarrangement of five color filters, 202, 204, 206, 208, 210,corresponding to five primary colors, respectively, on a color wheel200, in accordance with exemplary embodiments of the invention.

According to exemplary embodiments of the invention, color wheel 200 maybe part of a multi-primary color display device, for example, device 100described above.

According to embodiments of the invention, at least three of the colorfilters may be arranged on the color switching mechanism based on a hueorder of the primary colors. In this context, the hue order may be basedon the circumferential sequence of the primary colors on a chromaticitydiagram as is known in the art. According to the exemplary embodimentsof FIG. 2, a yellow filter segment 202 may extend between boundaries 201and 203 and may include a filter corresponding to a yellow spectralrange. A red filter segment 204 may extend between a boundary line 203and a boundary line 205 and may include a filter corresponding to a redspectral range. A blue filter segment 206 may extend between a boundaryline 205 and a boundary line 207 and may include a filter correspondingto a blue spectral range. A cyan filter segment 208 may extend between aboundary line 207 and a boundary line 209 and may include a filtercorresponding to a cyan spectral range. A green filter segment 210 mayextend between a boundary line 209 and a boundary line 201 and mayinclude a filter corresponding to a green spectral range.

A light beam 220 may be focused on color wheel 200, e.g., as describedabove. Light beam 220 may illuminate filter segments 202, 204, 206, 208and 210 when color wheel 200 is rotated, as described above. As lightbeam 220 passes from one color filter to an adjacent color filter, itmay illuminate parts of both color filters, e.g., parts of blue filter206 and red filter 204 may be illuminated when beam 220 passes overboundary 205. Thus, five-primary color wheel 200 may include fivetransition regions (“spokes”), in which light beam 220 illuminates twoadjacent color filters.

The size of each of the spokes may be related to a “spot size”, i.e., adiameter, of beam 220. For example, a blue-red spoke 234 between bluefilter 206 and red filter 204 may include the area between a boundaryline 224 and a boundary line 225; a red-yellow spoke 232 may include thearea between a boundary line 223 and a boundary line 222; a yellow-greenspoke 240 may include the area between a boundary line 221 and aboundary line 230; a green-cyan spoke 238 may include the area between aboundary line 229 and a boundary line 228; and a cyan-blue spoke 236 mayinclude the area between a boundary line 227 and a boundary line 226.

According to embodiments of the invention, some or all of the spokes maybe used to enhance the luminance of the primary colors, as describedbelow.

Controller 121 may be adapted to perform spoke recovery, i.e., to usethe light produced during some or all of the spoke periods, by providingthe SLM 106 with a input primary color image component related to thelocation of light beam 220 on color wheel 200, as described below.Controller 121 may use a synchronization system to coordinate betweenthe input signal and the location of the light beam.

According to exemplary embodiments of the invention, controller 121 mayprovide SLM 106 with five primary color image components, e.g., duringeach rotation of wheel 200. When light beam 220 illuminates a spoke,controller 121 may provide SLM 106 with a primary color image componentcorresponding to one of the two primary color filters adjacent to theilluminated spoke. The primary color image component to be provided tothe SLM in each spoke may be selected according to a viewed combinationof the colored light beams produced by two subsequent spokes. Forexample, a viewed combination of a red-yellow light beam and ayellow-green light beam produced when beam 220 illuminates spokes 232and 240, respectively, may be generally equivalent to a yellow color. Aviewed combination of a green-cyan light beam and a cyan-blue light beamproduced when beam 220 illuminates spokes 238 and 236, respectively, maybe generally equivalent to a cyan color produced by filter 208. Thus,for example, controller 121 may provide SLM 106 with yellow imagecomponent data when beam 220 illuminates spokes 232 and/or 240, and withcyan image component data when beam 220 illuminates spokes 238 and/or236. It will be appreciated that a blue-red color beam produced whenbeam 220 illuminates spoke 234 does not substantially affect the viewedblue image component. Thus, for example, controller 121 may provide SLM106 with blue image component data when beam 220 illuminates spoke 234.

According to the exemplary embodiments of FIG. 2, controller 121 mayprovide SLM 106 with an input signal corresponding to a yellow imagecomponent during a yellow electronic interval, i.e., when beam 220 is inthe region confined between boundaries 223 and 230; an input signalcorresponding to a green image component during a green electronicinterval, i.e., when beam 220 is in the region confined betweenboundaries 230 and 229; an input signal corresponding to a cyan imagecomponent during a cyan electronic interval, i.e., when beam 220 is inthe region confined between boundaries 229 and 226; an input signalcorresponding to a blue image component during a blue electronicinterval, i.e., when beam 220 is in the region confined betweenboundaries 226 and 224; and an input signal corresponding to a red imagecomponent during a red electronic interval, i.e., when beam 220 is inthe region confined between boundaries 224 and 222. Thus, the inputsignal provided to SLM 106 may include image components according to thefive electronic color intervals defined according to the regionsdescribed above.

According to some embodiments of the invention, SLM 106 may be of abinary modulation type. Examples of the binary modulation type include,but are not limited to, Digital Micro-mirror Device (DMD) andFerroelectric Liquid Crystal FLC, as are known in the art. The binarytype SLM may use Pulse Width Modulation (PWM) for creating gray levelsby controlling a luminance of a displayed primary color. This isachieved by controlling a display-period of the primary color, i.e., theSLM may display the primary color image component for a display periodduring a fraction of the electronic color interval. For example, inorder to display a yellow color having half of a maximal luminancevalue, SLM 106 may use the color light beam produced by color wheel 104to display the yellow image component during half of the electronicyellow interval.

According to embodiments of the invention, the electronic color intervalof some of the primary colors, e.g., yellow and cyan, may includeadjacent spoke periods, as described above. Thus, if a color isdisplayed for a period shorter than the electronic color interval, colormixing may occur, if the display-period includes unequal contributionsof the two spoke periods adjacent to the displayed color. For example, ayellow color having a display-period beginning in spoke 240 and endingbefore spoke 232 may be affected by the green contribution of spoke 240and not affected by the red contribution of spoke 232.

In order to minimize color mixing, at least some display-periods may bedistributed across the corresponding electronic color interval such thata substantially symmetrical contribution of the adjacent spoke periodsis achieved, as described below. For example, a yellow display-periodmay include symmetric contribution of the red-yellow and theyellow-green spoke periods, and a cyan display-period may includesymmetric contributions of the green-cyan and the cyan-blue spokeperiods. The symmetric contribution of the adjacent spoke periods may beaccomplished by independently controlling each digital valuecorresponding to a displayed image pixel, i.e., the digital value may betransformed into a time fraction, which may be within a correspondingelectronic color interval. This may be achieved, for example, bycontrolling, e.g., using controller 121, the beginning and the end ofthe SLM “on” mode of operation. For example, the digital value of eachpixel may be transformed, e.g., by controller 121, into two timingsignals, wherein one timing signal defines when to switch off acorresponding pixel of the SLM after the beginning of the electroniccolor interval, and the second timing signal defines when to switch thesame SLM pixel on again before the end of the electronic color interval.

In fully digital display systems, a timing sequence for displaying eachpixel may be digitized, i.e., the pixels may be turned on and off atpre-defined times. In such systems, the input signal provided to theSLM, e.g., by the controller, may be divided into bit planes, and eachbit plane may be provided to the SLM for a time period corresponding tothe significance of the bit plane. For example, the most significant bitmay be provided to the SLM, e.g., by the controller, for half of theelectronic color interval, the second-most significant bit may beprovided to the SLM for a quarter of the electronic color interval, andso on, such that the i-th most significant bit plane may be provided tothe SLM for 2^(−i) of the electronic color interval. In manyapplications, the higher significance bit planes may be further dividedinto sub-bit planes in order to smooth transitions between bit planes.Each bit plane is related to a predefined time slot, corresponding to adifferent fraction of the electronic color interval, e.g., the time slotof the most significant bit plane may correspond to the first half ofthe electronic color interval. Thus, each required display-period may bea combination of one or more of the bit planes. For example, adisplay-period of 129/255 may correspond to a combination of the mostsignificant bit plane (128/255) and a least significant bit plane(1/255).

In such systems, the spoke period may be much larger than the time slotof the least significant bit plane. Thus, if the least significant bitplane corresponding to a primary color, e.g., yellow, is related to anadjacent spoke period, e.g., red-yellow, the color, e.g., red, of theleast significant bit plane may be different from the color, e.g.,yellow, of the other bit planes, resulting in potential color errors.

According to exemplary embodiments of the invention, the bit planes ofthe highest significance may be related to the spoke periods. Accordingto one exemplary embodiment, the most significant plane may be splitbetween the two sides of the electronic color interval. Thus, the twoadjacent spokes may be included in the most significant bit plane, e.g.,for a display period equal to or shorter than 127/255 neither of thespoke periods may be used, and for a display period equal to or longerthan 128/255 both spoke periods may be used. Therefore, opposing colorshifts produced by the spokes, e.g., red-yellow and green-yellow shifts,may substantially cancel each other out when viewed, as described above.Furthermore, since the most significant bit plane covers the largestfraction of the electronic color interval, the influence of the spokeson the viewed color is further minimized.

Some display devices may not support the splitting of the mostsignificant bit plane described above. Therefore, according to furtherexemplary embodiments of the invention, the most significant plane maybe related to one end of the electronic color interval and thesecond-most significant bit plane may be related to the other end. It isappreciated that this arrangement may cause a shift in chromaticityand/or luminance. Such a shift, which may be a function of gray level,is mostly minor and may generally be ignored. However, if a highaccuracy of color reproduction is required, these minor changes may becorrected by performing an inter-color gamma adjustment, as describedbelow.

Reference is made to FIG. 3, which illustrates a block diagram of anexemplary implementation of a method of inter-color gamma adjustmentaccording to an exemplary embodiment of the invention.

As indicated at block 310, the inter-color gamma adjustment may includedetermining a value of the most significant bit and the second-mostsignificant bit of a primary color signal 302 and, according to thesevalues, producing a signal 303 identifying which of the adjacent primarycolors is to be corrected.

According to signal 303, a correction signal for an adjacent primarycolor 304 may be produced, as indicated at block 320. The correctionsignal may be determined by a calculation or a look-up-table.

The correction signal may be added to an adjacent primary color 304 toproduce a corrected signal 306, as indicated at block 330.

For example, the most significant bit plane related to the electronicyellow interval may be related to the yellow-green spoke, and the secondmost significant bit may be related to the red-yellow spoke. Thus, forany pixel having a yellow input signal in the range of 128-255, whereinthe most significant bit equals 1 and the least significant bit equalszero (in an 8 bit/primary system), the red data (primary 2) of the pixelmay be adjusted to compensate for a slight green shift. Accordingly, forany pixel with a yellow input signal in the range of 64-127, wherein thesecond most significant bit equals 1 and the most significant bit equalszero, the green data (primary 1) of the pixel may be adjusted tocompensate for a slight red shift.

According to yet further exemplary embodiments of the invention, theelectronic color interval may be divided into a plurality of bit planessuch that a small fraction, at the most, of the display period mayinclude a fraction of the spoke periods, as described below. Each bitplane may be related to a predefined time slot, corresponding to adifferent fraction of the electronic color interval such that at leastsome, e.g., all, bit planes corresponding to fractions of the spokes(“spoke bit planes”) are related to a substantially small time slot,some bit planes corresponding to fractions of the electronic colorinterval not including the spokes (“non-spoke bit planes”) are relatedto a substantially large time slot, and some non-spoke bit planes arerelated to a substantially small time slot. A threshold value may bepre-selected such that display periods equal to or smaller than thethreshold value may be related with at least some non-spoke bit planes,and display periods bigger than the threshold value may be related withat least some, e.g., all, the non-spoke bit planes and with at leastsome of the spoke bit planes. The threshold value may be selected assubstantially the fraction of the electronic color interval notincluding the spokes out of the total electronic color interval. Thus,color variations due to the spoke periods may be minimized, since eachdisplay period is at least mostly related to non-spoke bit planes.

Reference is also made to FIG. 4A, which schematically illustratesgraphs of five exemplary primary color wavelength spectra for a colordisplay using the color wheel of FIG. 2, and to FIG. 4B, whichschematically illustrates chromaticity diagrams representing a colorgamut 402 resulting from the five primary color spectra of FIG. 4A whenspoke recovery is implemented, compared to a color gamut 404 resultingfrom the five primary color spectra of FIG. 4A when spoke recovery isnot implemented.

As clearly shown in FIG. 4B, color gamut 404 is substantially covered bycolor gamut 402. The luminance values for the colors obtained for adisplay implementing spoke recovery is about 25% higher than theluminance value obtained for the same colors from a five-primary displaynot implementing spoke recovery, e.g., by turning the SLM to an “off”mode of operation during the transition time between two adjacent colorfilters.

It may be appreciated by those skilled in the art, that themulti-primary display device according to embodiments of the inventionmay implement spoke recovery to enhance luminance values of primarycolors. It may further be appreciated that the display device accordingto embodiments of the invention may implement spoke recovery withoutrequiring calculation of any additional image components, for example,white image components and/or secondary color image components.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1. A display device for producing a color image including at least fournon-white colors comprising: a color wheel including at least fournon-white color filters, each having a respective non-white color; acontroller to control a spatial light modulator to produce at least fourcolor image components, each color image component corresponding to acolor of said non-white color filters during a respective displayperiod, at least a first of said display periods including a first spokeperiod corresponding to illumination of a first non-white color filterand at least a sequentially adjacent portion of a second spoke periodcorresponding to illumination of a second color filter.
 2. The device ofclaim 1, wherein said first display period further comprises at least aportion of a third spoke period corresponding to illumination of a thirdcolor filter of said non-white color filters, said portion of the thirdspoke period sequentially adjacent to said first spoke period.
 3. Thedevice of claim 2, wherein said first display period has a desireddistribution between the spoke period of said first and second colorfilters and the spoke period of said first and third color filters. 4.The device of claim 3, wherein said first display period is distributedgenerally symmetrically between the spoke period of said first andsecond color filters and the spoke period of said first and third colorfilters.
 5. The device of claim 2, wherein said first display period isrepresented by a plurality of bit planes including one or more highestsignificance bit planes, and wherein one or more of said highestsignificance bit planes correspond to at least one of the spoke periodof said first and second color filters and the spoke period of saidfirst and third color filters.
 6. The device of claim 5, wherein a mostsignificant bit plane of said one or more highest significance bitplanes corresponds to both the spoke period of said first and secondcolor filters and the spoke period of said first and third colorfilters.
 7. The device of claim 5, wherein a most significant bit planeof said one or more highest significance bit planes corresponds to afirst end of an electronic color interval including the spoke period ofsaid first and second color filters, and a second-most significant bitplane of said one or more highest significance bit planes corresponds toa second end of said electronic color interval including the spokeperiod of said first and third color filters.
 8. The device of claim 5,wherein said controller is able to control said spatial light modulatorto produce a corrected succeeding color image component corresponding tosaid third color filter based on a value of a most significant bit planeand a second-most significant bit plane of said one or more highestsignificance bit planes.
 9. The device of claim 2, wherein said firstdisplay period is represented by a plurality of bit planes including atleast one spoke bit plane corresponding to at least one of the spokeperiod of said first and second color filters and the spoke period ofsaid first and third color filters, wherein said at least one spoke bitplane represents a time period shorter than a predetermined time periodthreshold.
 10. The device of claim 2, wherein said controller is able tocontrol said spatial light modulator such that a viewed combination ofcolored light of the spoke period of said first and second color filtersand colored light of the spoke period of said first and third colorfilters is generally equivalent to said first color filter.
 11. Thedevice of claim 2, wherein said first, second and third color filtersare yellow, green and red, respectively.
 12. The device of claim 2,wherein said first, second and third color filters are cyan, green andblue, respectively.
 13. The device of claim 2, wherein said first,second and third color filters are magenta, blue and red, respectively.14. The device of claim 1, wherein said color filters are arrangedsequentially according to their hue values.
 15. The device of claim 1,wherein said first display period comprises at least most of the spokeperiod of said second color filter.
 16. A method for producing a colorimage using a color wheel including at least four non-white colorfilters, each having a respective non-white color, said methodcomprising: producing at least four color image components, each colorimage component corresponding to a color of said non-white color filtersduring a respective display period, at least a first of said displayperiods including a first spoke period corresponding to illumination ofa first non-white color filter and at least a sequentially adjacentportion of a second spoke period corresponding to illumination of asecond color filter.
 17. The method of claim 16, wherein said firstdisplay period further comprises at least a portion of a third spokeperiod corresponding to illumination of a third color filter of saidnon-white color filters, said portion of the third spoke periodsequentially adjacent to said first spoke period.
 18. The method ofclaim 17, wherein said first display period has a desired distributionbetween the spoke period of said first and second color filters and thespoke period of said first and third color filters.
 19. The method ofclaim 18, wherein said first display period is distributed generallysymmetrically between the spoke period of said first and second colorfilters and the spoke period of said first and third color filters. 20.The method of claim 17, wherein said first display period is representedby a plurality of bit planes including one or more highest significancebit planes, and wherein one or more of said highest significance bitplanes correspond to at least one of the spoke period of said first andsecond color filters and the spoke period of said first and third colorfilters.
 21. The method of claim 20, wherein a most significant bitplane of said one or more highest significance bit planes corresponds toboth the spoke period of said first and second color filters and thespoke period of said first and third color filters.
 22. The method ofclaim 20, wherein a most significant bit plane of said one or morehighest significance bit planes corresponds to a first end of saidelectronic color interval including the spoke period of said first andsecond color filters, and a second-most significant bit plane of saidone or more highest significance bit planes corresponds to a second endof said electronic color interval including the spoke period of saidfirst and third color filters.
 23. The method of claim 20 comprisingproducing a corrected succeeding color image component corresponding tosaid third color filter based on a value of a most significant bit planeand a second-most significant bit plane of said one or more highestsignificance bit planes.
 24. The method of claim 17, wherein said firstdisplay period is represented by a plurality of bit planes including atleast one spoke bit plane corresponding to at least one of the spokeperiod of said first and second color filters and the spoke period ofsaid first and third color filters, wherein said at least one spoke bitplane represents a time period shorter than a predetermined time periodthreshold.
 25. The method of claim 17, wherein producing a color imagecomponent comprises producing said color image component such that aviewed combination of colored light of the spoke period of said firstand second color filters and colored light of the spoke period of saidfirst and third color filters is generally equivalent to said firstcolor filter.
 26. The method of claim 17, wherein said first, second andthird color filters are yellow, green and red, respectively.
 27. Themethod of claim 17, wherein said first, second and third color filtersare cyan, green and blue, respectively.
 28. The method of claim 17,wherein said first, second and third color filters are magenta, blue andred, respectively.
 29. The method of claim 16, comprising sequentiallyproducing colored light of a plurality of colors.
 30. The method ofclaim 29, wherein sequentially producing colored light comprisessequentially passing light through said plurality of non-white colorfilters corresponding to said plurality of non-white colors,respectively.
 31. The method of claim 30, wherein the illuminationsequence of said filters is according to their hue values.
 32. Themethod of claim 16, wherein said first display period comprises at leastmost of the spoke period of said second color filter.
 33. A displaydevice for producing a color image including at least four non-whitecolors comprising: a light source to sequentially illuminate at leastfirst, second, third and fourth non-white color filters of a colorswitching mechanism; a spatial light modulator to modulate colored lightof said color wheel in accordance with four or more non-white colorimage component signals, said color image component signalscorresponding to said non-white color filters, respectively; and acontroller to sequentially generate said four or more non-white colorimage component signals during four or more electronic color intervals,respectively, wherein at least a first of said electronic colorintervals includes a first spoke period corresponding to illumination bysaid light source of the corresponding first non-white color filter andat least a portion of a second spoke period corresponding toillumination by said light source of the corresponding second non-whitecolor filter.
 34. The device of claim 33, wherein said first electroniccolor interval further includes at least part of a third spoke periodcorresponding to illumination by said light source of the correspondingthird non-white color filter.